JP2012053792A - System for reducing usb isochronous transfer error - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide "a system for reducing USB isochronous transfer error", capable of easily preventing a trouble due to the occurrence of a communication error without largely modifying a conventional transfer system when performing USB isochronous transfer.SOLUTION: When performing USB isochronous transfer for transmitting and receiving data which does not have a function to notify a communication error, by designating a device to perform communication to an arbitrary microframe and recording the data in accordance with a USB2.0 specification where another device is connected to a host device by a USB cable and one frame includes a plurality of microframes, same data for the same device are recorded in the plurality of microframes of the one frame to be transmitted and received. Therefore, the communication error can be covered by another data even when one data generates the error. This data format may be employed when it is detected that the connection device has a history of generating the communication error before.

Description

  The present invention relates to a USB isochronous transfer error reduction system capable of reducing the occurrence of errors during isochronous transfer in USB connection.

  USB (Universal Serial Bus) is an interface standard that allows various peripheral devices to be connected using a common connector by providing a host controller inside a personal computer or the like. When USB is used, many devices can be connected by adding a branch point called a hub.

  When peripheral devices are connected or software expansion parts are installed, operations such as installing device drivers or setting dip switches are usually required. USB is a so-called plug and play (Plug and Play). It supports hot plug that can recognize the device in (Play). In other words, when peripheral devices are connected using USB, IRQ (Interrupt ReQuest) and I / O (Input / Output) addresses are used so that anyone can easily connect without any setting operations. Since system resource values such as DMA (Direct Memory Access) channels are automatically set so as not to collide with other peripheral devices, these peripheral devices can be used immediately.

  At present, the USB interface mounting rate in personal computers is almost 100%, and it can be said that it has become established as a standard interface between personal computers and peripheral devices. Accordingly, peripheral devices having a USB interface are also widely used.

  Due to the widespread use of USB devices, in addition to personal computers, for example, a head unit mounted on a vehicle has a USB connection host controller function and a USB terminal so that, for example, a USB memory can be directly inserted. Peripheral devices that can be connected via USB can be connected and used. As a result, the MP3 audio data recorded on the USB memory can be listened to, and the audio data recorded on the data recording medium of the portable audio player can be captured and listened to with a high-performance audio device provided in the vehicle. Be able to.

  When performing USB connection, peripheral devices are connected by a unified connector, and data transfer of all USB devices is executed by time-sharing the same protocol bus. In other words, the basic protocol is the same for all USB peripheral devices, so in order to cope with the unique characteristics of many devices, four types of data transfer methods are prepared. Select or use them in combination.

  In other words, the USB provides four types of transfer methods: interrupt transfer, bulk transfer, control transfer, and ISO (isochronous) transfer. Each peripheral device can realize optimal communication by selecting a transfer method suitable for its own operating characteristics. Two types of data rates are supported for USB 1.x: 12 Mbps Full-Speed and 1.5 Mbps Low-Speed, and USB 2.0 further supports higher 480 Mbps High-Speed. Has been.

  Of the four types of transfer methods, interrupt transfer is a data transfer method that is periodic and has a low bandwidth. For example, in an input device such as a mouse, keyboard, joystick, etc. It is required to process the input data within the time, and it is a transfer method suitable for such a device.

  Bulk transfer is a transfer method that handles a large amount of data aperiodically, and is used when high reliability is required for data transfer. For example, an output device for inputting or printing an image such as a printer, a scanner, or a digital still camera, a memory card reader, a flexible disk drive, a CD-ROM (Compact Disc Read Only Memory) drive, a CD-R (Compact A storage-type device such as a disc recordable drive is suitable for a device that is required to transfer large-scale data accurately (without data loss).

  Control transfer is a transfer method used for exchanging information necessary for controlling peripheral devices. Unlike the transfer methods of interrupt transfer, bulk transfer, and isochronous transfer, control transfer is also defined for the transferred data itself. Yes. That is, the control transfer is used for device information exchange, address setting under the USB environment, or device setting. Therefore, this transfer method is always used for any device.

  In contrast to the above-described transfer methods in USB, isochronous transfer is a transfer method used when real-time performance is required. In an apparatus that handles audio, such as an audio device, a microphone, and a telephone, It is required to reflect the concept of time correctly, that is, to send a certain amount of data during a certain period.

  The most important thing in isochronous transfer is to transfer a certain amount of data in a certain cycle. Therefore, retransmission due to transfer failure is not performed because it makes it difficult to maintain the concept of time. That is, even when data is not transferred correctly, the next data is transferred in the next cycle. Therefore, in isochronous transfer, even if data is missed, re-transfer is not performed, so handshake packets provided by other transfer methods are not used. Therefore, even if a communication error occurs, the data to be corrected is not transmitted, so the error remains generated.

  In data transfer in USB isochronous transfer, multiple reception endpoints are set, the same data is transmitted in different packets, the data of packets communicated correctly is connected, the print data is reproduced, and printing is performed. A technique for avoiding job cancellation and job retransmission due to a communication error is disclosed in Patent Document 1. Also, during USB isochronous transfer, the print data is divided so as to have a packet size set by the USB interface with a header added, and the packet data is copied to create a plurality of packets of the same data. Patent Document 2 discloses a technique in which numbers are assigned to print data by connecting only correctly received data without using a data error packet.

JP 2003-345541 A JP 2004-54504 A

  As described above, USB isochronous transfer does not retransmit data even if it is known that a communication error has occurred. For example, a slight transfer error occurs during communication, such as video or audio. However, it is almost unknown to human senses, and it is most suitable for the transfer method in equipment that is more worried about temporal data shift.

  However, for example, various devices have recently been connected to a head unit, which is a central device such as a vehicle audio device, and the portable audio device has become particularly popular due to the widespread use of portable audio devices capable of recording a large amount of data. The music is often listened to by a high-performance audio system connected to the head unit. At that time, a USB host function that controls operation by connecting a USB device to the head unit is increasing. At that time, a portable audio device having a USB connection function is connected to the head unit with a USB cable, and the data of the portable audio device is captured by an operation on the head unit side, and is reproduced and listened.

  At that time, the data of the portable audio device is transferred to the head unit side by USB isochronous transfer. However, the data is transferred from the portable audio device due to the performance of the device or the occurrence of a transfer error in the connection cable. A transfer error occurs in the data. It is good if the error at that time is very temporary, but if this occurs frequently to a certain extent, a high-performance vehicle audio device will be used, and especially for those who are sensitive to hearing, annoying sound interruptions and abnormal noise may occur. This can cause distrust to this audio device for those who want to hear high performance audio.

  On the other hand, in order to solve the above-mentioned problems of isochronous transfer, various corresponding techniques have been proposed. In the technique of the above-mentioned Patent Document 1, which is a countermeasure technique, the technique is proposed as a countermeasure technique when transmitting print data by isochronous transfer. This technique is a space that can be shared between the host and the connected device. This is a method of connecting a plurality of endpoints and connecting data, and it is necessary to greatly change the conventional data transfer form, and the software for that must be complicated.

  Similarly, the technique disclosed in Patent Document 2, which is a technique for solving the same problems, is a technique for greatly changing the conventional communication method, and therefore, the software needs to be significantly changed. In other words, token packets and data packets exist in isochronous transfer, and the token packet is a signal for sending a request from the host side to the connected device side, and the data packet is data transmitted from the connected device side to the host. In a frame that is an aggregate, only the data within the specified range can be transmitted to the packet at the maximum, so that the conventional transmission method needs to be greatly changed to adopt the method described in this patent document.

  Therefore, the present invention does not impede the characteristic of transferring a certain amount of data in a certain period, which is a characteristic of isochronous transfer, and does not greatly change the conventional transfer method when performing USB isochronous transfer. The main object of the present invention is to provide a technique capable of easily preventing inconvenience due to the occurrence of a communication error without greatly changing the conventional isochronous transfer software.

  The USB isochronous transfer error reduction system according to the present invention connects a host device to another device with a USB cable, includes a plurality of microframes in one frame, and designates a device that performs communication in an arbitrary microframe. In a USB isochronous transfer error reduction system that transmits and receives isochronous transfer data that does not have a function of notifying a communication error in the data, the same data of the same device is recorded in a plurality of micro frames of one frame. It is characterized by requesting the connected device to transmit.

  Another USB isochronous transfer error reduction system according to the present invention is the USB isochronous transfer error reduction system, wherein the host device has communication error data storage means for recording the number of communication errors for each device connected to the host device, and Search means for searching for a communication error of a device connected to the host device using the communication error storage means, and when detecting that the device connected by the search means has previously caused a communication error, the host device An output for requesting a connected device to record and transmit the same data of the same device in a plurality of micro frames of the one frame is performed.

  In another USB isochronous transfer error reduction system according to the present invention, in the USB isochronous transfer error reduction system, the number of microframes that record the same data increases as the number of errors searched by the search means increases. A request is made to record the same data.

  Another USB isochronous transfer error reduction system according to the present invention is the USB isochronous transfer error reduction system, wherein the host device includes a data storage unit for recording and storing a device connected to the host device, and the data storage unit. A search unit that searches for a connection record of a device connected to the host device, and when the search unit detects that the connected device is connected to the host device for the first time, A request is made to record and transmit data in a frame.

  In another USB isochronous transfer error reduction system according to the present invention, in the USB isochronous transfer error reduction system, the microframes that record the same data of the same device are all the microframes that do not record other data. It is characterized by that.

  Since the present invention is configured as described above, when performing USB isochronous transfer, the conventional transfer method is greatly increased without obstructing the characteristic of transferring a certain amount of data in a certain period, which is a characteristic of isochronous transfer. It is possible to easily prevent the occurrence of a communication error without changing, and thus without greatly changing the conventional isochronous transfer software.

It is a functional block diagram of the Example of this invention. It is an operation | movement flowchart of the Example. It is a figure explaining the format of the transmission / reception data of this invention. It is a figure which shows the example of transmission / reception data by the Example of this invention.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a functional block diagram of a USB isochronous transfer error reduction system according to the present invention. In the illustrated example, a system configuration is shown in which a head unit mounted on a vehicle and a portable audio device are connected with a USB cable, audio data of the portable audio device is taken into the head unit, and this is reproduced and listened.

  The head knit shown in FIG. 1 includes a USB host control unit 3 that controls the entire USB connection function when the devices are connected to each other with the USB cable 23. Therefore, the head unit becomes the host device 1, and this host The portable audio device connected to the device 1 becomes the connection device 2 connected to the host device.

  The USB host control unit 3 provided in the host device includes a connection device recognition unit 4 that performs an operation of recognizing each other device by USB software when connecting to the connection device 2 with the USB cable as described above. ing. In addition, a transmission / reception data management unit 5 is provided, and a transmission data creation unit 6 in the transmission / reception data management unit 6 identifies peripheral devices, transmits data, and creates data to be transmitted. The transmission data created here is transmitted from the USB communication unit 13 to the connection device 2 in the illustrated example via the USB cable 23.

  When the transmission data format request unit 7 receives data from the connected device 2 as will be described later, the format of the transmission data is a single microframe transmission data format (A) 9 which is a normal transmission data format. The transmission data format selection unit 8 selects one of a plurality of microframes having the same transmission data format (B) 10, and the transmission data format request unit 7 outputs a request to the connected device according to the selection. This request signal is also transmitted from the USB communication unit 13 to the connected device 2.

  The transmission data format selection unit 8 searches the data in the communication error data storage unit 11, and in particular the device connected with the current USB cable from the data in the data storage unit of the number of errors for each connected device in the communication error data storage unit 11. One of the transmission data formats is selected depending on whether or not a past communication error exists.

  That is, when the connection device 2 is connected to the host device 1 with the USB cable 23, it is detected that the device connected this time has been connected before, and that there was a communication error when connected previously. The data format of the same transmission data format (B) for a plurality of microframes is selected. In other cases, the single microframe transmission data format 9, which is a normal USB data format, is selected.

  The single microframe transmission data format (A) selected by the transmission data format selection unit 8 in FIG. 1 is, as shown in FIG. 3, for one frame which is a unit divided every 1 ms according to the USB standard, in particular, USB2. In 0, this is further divided into 8 microframes by 125 μs, different connected devices are designated in each microframe, and data within a predetermined amount is transmitted.

  Therefore, when there is only one connected device as shown in FIG. 1, as shown as data format (A) in FIG. 3, data is selected by selecting any one of the 8 microframes. Record and send to the host device. The example of the data format (A) in FIG. 3 shows an example in which the data D1 is recorded and transmitted in the first microframe (MF1). As for the microframe, as with USB 1.1, various data including device designation data are recorded. However, during isochronous transfer, the data was received correctly or could not be received. There is no handshake data to contact.

  On the other hand, for the same micro-frame transmission data format (B) in FIG. 1, for example, as shown as data format (B2) in FIG. 3, and as shown as data format (B) in FIG. The same data is recorded in all the microframes and transmitted. In this example, since there is only one connected device for the host device, the same data can be recorded in all microframes.

  Therefore, when there are a plurality of connected devices and each transmission data is in a microframe of the same frame, a microframe in which no data is recorded is selected and the same data is recorded in all of them. By transmitting such data, the receiving side can perform operations such as audio reproduction using any data as long as all data does not cause a communication error.

  When the same transmission data format (B) of a plurality of microframes as described above is adopted, in addition to recording the same data in all the microframes in which no data is recorded in one frame, for example, FIG. 3 (B1) As shown in FIG. 5, by recording the same data in an arbitrary plurality, it becomes possible to transmit data more reliably than the conventional data format such as the data format (A). In the example shown in FIG. 3, when data is recorded and transmitted only in the first microframe MF1 as in the conventional data format (A), the second to fourth microframes are used. In this example, the same data D1 is recorded and transmitted in MF2, MF3, and MF4.

  Even in the above case, when a plurality of connected devices are connected to the host device and each piece of data is transmitted by a microframe in the same frame, the same data is recorded in a microframe in which no data is recorded. It will be. When the data format (B) is adopted as described above, the amount of data during communication increases, so in the example of FIG. 1, the data in the communication error data storage unit 11 is used to generate a communication error before. Only that data format is adopted. Further, when it is detected from the separately recorded connected device data that the device connected this time is connected to the host device for the first time, the conventional data format (A) may be adopted.

  Furthermore, when the connected device is first connected, transmission is performed in the data format (A), and then when the host device detects that a communication error has occurred with respect to the received data, subsequent data is transmitted to the connected device. You may request to transmit in the format (B). Further, when it is detected that a communication error has not occurred for a predetermined time thereafter, the previous communication error is presumed to have occurred due to a special environment, and a request is made to transmit in the normal data format (A). You can also Such selection can be arbitrarily selected by the transmission data format selection unit 8 in various ways.

  When the USB host control unit 3 of the host device 1 having the above functions exists, the connected device side performs processing corresponding to the request. In the USB connection device controller 14 of the connection device 2 shown in FIG. 1, when the connection device is connected to the host device 1 via the USB cable 23, the USB communication unit 22 starts communication with the host device 1, and the device recognition unit 15 recognizes the host device 1 connected this time.

  The transmission data creation unit 17 in the transmission / reception data management unit 16 creates data to be transmitted. In particular, transmission is performed in one of the formats selected by the transmission data format selection unit 18. Create the data to do. In this transmission data format selection unit 18, the request of the transmission data format request unit 7 transmitted from the host device 1 by the USB communication unit 22 from the bag is received by the creation data format reception unit 21, and corresponding to the format, As described above, one of a single microframe transmission data format (A) and a plurality of microframe same communication data format (B) is selected.

  When creating such data, particularly in the case of the same transmission data format (B) of a plurality of microframes, data can be transmitted in various modes as shown in FIG. All are performed at the request of the USB host control unit 3 side of the host device 1 side.

  The side receiving the data in which the same data is recorded in such a plurality of microframes opens the data of one of the microframes, does not perform any further processing when no error has occurred, and if an error has occurred. In such a case, the next arbitrary microframe data is selected and opened, and when no error has occurred, no further processing is performed, so that unnecessary data processing burden is not applied. can do.

  In the system of the present invention configured as described above, the present invention can be operated by the operation flow shown in FIG. 2, for example. The data processing for USB isochronous transfer in FIG. 2 starts by connecting the USB device to the USB host device first (step S1), and then determines whether the connected USB device is compatible with USB 2.0. That is, in the present invention, as described above, the USB 2.0 function in which a plurality of microframes exist in one frame is used. Therefore, in the illustrated example, the connected device has the USB 2.0 function. It is determined whether or not a function of transmitting data in a microframe is provided.

  When it is determined in step S2 that the connected device is not compatible with USB 2.0, the subsequent operation is not performed, and a further USB device connection is awaited. If it is determined in step S2 that the connected device is compatible with USB 2.0, recognition data is acquired between the connected devices (step S3). This function is automatically performed according to the normal USB standard. Thereafter, in the example of FIG. 2, the connected device determines whether or not to perform isochronous transfer.

  As described above, this determination is performed at a constant cycle, such as an audio device, among the four types of transfer methods of interrupt transfer, bulk transfer, control transfer, and isochronous transfer. It is determined by recognizing that it is set as a device that performs isochronous transfer because it is a device that preferably transfers a certain amount of data.

  When it is determined in step S4 that the connected device does not perform isochronous transfer, the process returns to step S1 to wait for a new USB device to be connected. When it is determined in step S4 that the connected device is to perform isochronous transfer, the connected device information is obtained from the connection recognition data (step S5), and it is determined whether or not the connected device is connected to the host device for the first time. (Step S6).

  This operation can be detected by accumulating recognition data of a device connected to the host device that has been provided so far in the host device. Here, when it is determined that the device is connected for the first time, the process proceeds to step S10, and the connection device is requested to transmit data in one microframe, which is a conventional data format.

  On the other hand, when it is determined that the host device has been connected before, the past communication error count of the connected device is searched from the communication error data for each USB connected device (step S7). Thereafter, in step S8, the connected device determines whether or not a communication error has occurred in the past, and when it is determined that a communication error has occurred before, the same data as the data format (B) Request the connected device to transmit in microframe. At this time, the micro data recording the same data may record the same data in more micro frames as the number of errors increases.

  When it is determined in step S8 that the connected device is not connected for the first time as described above and no communication error has occurred in the past, the process proceeds to step S10, and the conventional format is used as described above. The data is transmitted in one microframe.

  The present invention can be implemented by the operation flow as described above by the functional block as described above. As a result, for example, data as shown in FIG. 4 is formed. The example shown in the figure is a diagram showing the result of analyzing USB data during communication. FIG. (A) shows the conventional format (A), and (b) shows the same data recorded in all frames. An example when it is transmitted is shown. In the conventional format shown in FIG. 5A, data is recorded and transmitted in the eighth micro frame (MF8), and there is no other data to be transmitted.

  The state in which only one USB cable is connected to such a host device is a normal state in the head unit mounted on a vehicle as described above, and when a plurality of devices are automatically connected by the Bluetooth function, the vehicle is boarded. Although frequently caused by automatic connection with people's mobile phones and portable audio devices, it is extremely rare to connect a plurality of devices to a host device via a USB cable. For this reason, in most cases, the microframe function provided in USB 2.0 is not used. Accordingly, the present invention has been achieved by paying attention to such a point.

  FIG. 4B shows an example of the data format (B), and shows an example in which the same data is recorded and transmitted in all the microframes. The example of FIG. 7B shows an example in which the data of the eighth micro frame (MF8) is recorded in all the first to seventh micro frames in the example of FIG.

DESCRIPTION OF SYMBOLS 1 Host apparatus 2 Connection apparatus 3 USB host control part 4 Connection apparatus recognition part 5 Transmission / reception data management part 6 Transmission data creation part 7 Transmission data format request part 8 Transmission data format selection part 9 Single micro frame transmission data format (A)
10 Multiple microframes same transmission data format (B)
11 Communication error data storage unit 12 Error count data storage unit for each connector 13 USB communication unit 14 USB connection device control unit 15 Host device recognition unit 16 Transmission / reception data management unit 17 Transmission data creation unit 18 Transmission data format selection unit 19 Single micro Frame transmission data format (A)
20 Multiple microframes same transmission data format (B)
21 Created data format reception unit 22 USB communication unit 23 USB cable

Claims (5)

Connect another device to the host device with a USB cable,
USB isochronous that includes multiple microframes in one frame, records data by specifying a device that communicates in any microframe, and transmits and receives isochronous transfer data that does not have a function of notifying a communication error in the data In the transfer error reduction system,
A USB isochronous transfer error reduction system which requests a connected device to record and transmit the same data of the same device in a plurality of micro frames of one frame. The host device has communication error data storage means for recording the number of communication errors for each device connected to the host device, and
Search means for searching for communication errors of a device connected to a host device using the communication error storage means,
When the device connected by the search means detects that a communication error has occurred before, the host device records and transmits the same data of the same device in a plurality of microframes of the one frame. The USB isochronous transfer error reduction system according to claim 1, wherein an output requested by the device is performed.   3. The USB isochronous transfer error reduction according to claim 2, wherein the micro-frame recording the same data makes a request to record the same data in more micro-frames as the number of errors searched by the search means increases. system. Data storage means for recording and storing a device connected to the host device in the host device,
Search means for searching for connection records of devices connected to the host device using the data storage means,
2. A request for recording and transmitting data in a single microframe when the search means detects that the connected device is connected to the host device for the first time. USB isochronous transfer error reduction system.   2. The USB isochronous transfer error reduction system according to claim 1, wherein the microframes that record the same data of the same device are all microframes that do not record other data.

Images